Tray Efficiency Research Articles

An Intelligent Tray Efficiency Estimation Method for the Fractionation System of Industrial Hydrocracking Processes

AbstractAn engineering‐oriented tray efficiency estimation method for the hydrocracking fractionation system is proposed. As key parameter of the fractionation system, estimation of the tray efficiency is important and challenging due to the large computational burden given by the complexity of the fractionation system. Here, the high‐dimensional tray efficiencies are screened first and divided into groups according to the spatial position. Then, an improved artificial bee colony algorithm is proposed to estimate the tray efficiencies of each group, in which two taboo lists are introduced to avoid repetitive search. The proposed method is validated using real industry data. The results demonstrate that the proposed approach is efficient in terms of estimation accuracy.

A new simplified tray efficiency model with improved accuracy for sieve trays

Engineers rarely use modern tray efficiency models due to the high effort required implementing them and due to their lack of accuracy. The more rigorous traditional models require many input parameters; newer mechanistic models increase the complexity even further. In sharp contrast, O’Connell’s empirical but simple correlation is widely applied despite its shortcomings.We will present a simplified model based on the traditional approach that allows a process engineer to estimate the tray efficiency during the hydraulic design phase, when an equilibrium stage simulation is available. Despite the simplifications, the new model achieves improved accuracy at predicting the section efficiencies when compared to both the O’Connell method and to more rigorous (and complicated) modern methods.

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Computer models must be based on an existing plant's operations. Otherwise, key variables such as:•Relative volatility•Tray efficiencies•Exchanger fouling factorshave to be guessed at, without a firm basis.Tray efficiency, for example, is largely a function of tray deck levelness and overflow weir levelness, which are largely unknown to the designer. Thus, a computer model is at best, just an educated guess or approximation of reality.

Development of a Refined RTD-Based Efficiency Prediction Model for Cross-Flow Trays

The present work describes the mathematical formulation of a new tray efficiency model through refinement of the conventional residence time distribution (RTD) approach [Foss et al. AIChE J. 1958, ...

A Novel RTD Compartment Model for Tray Efficiency Predictions

In the present work, a new model built through refinement of the existing residence time distribution model [Foss, PhD Thesis, University of Delaware, 1957] is proposed. In this new model, the tray is imaginarily partitioned into compartments along the liquid flow direction between inlet and outlet. This partitioning allows computing the tray efficiency through quantification of the efficiencies of the individual compartments. Therefore, the fluid dynamics of each compartment contribute towards the evolving tray efficiency, thereby breaking the tray’s black-box convention. The tray segmentation further supports in studying the effects of vapor maldistribution as well as flow path length on the tray efficiency. This indicates the versatility and advantage of the new model over the existing ones. In particular, the mathematical formulation of this model along with its theoretical validation and application through analysis of suitable case studies are presented.

A New Tray Efficiency Model: How Simple May It Be?

Engineers rarely apply the most rigorous tray efficiency models due to the significant effort required to implement them and due to their relative lack of accuracy. Rigorous traditional models require a good deal of information; and mechanistic models increase the complexity even further. In sharp contrast, O’Connell’s empirical but simple correlation is widely applied despite its shortcomings.This paper presents a simplified model based on the traditional approach that allows a process engineer to estimate the tray efficiency for sieve trays during the hydraulic design phase, when an equilibrium stage simulation is available. Despite the simplifications, the new model is more accurate than more modern methods and the O’Connell method.

C 2 Splitter Revamp Surpasses Capacity and Efficiency of 4-Pass Trays

A C2 Splitter in Norco, Louisiana was successfully revamped with Shell HiFi™ Plus trays in 2015 for increased tray capacity. The HiFi Plus tray is a joint development between Sulzer and Shell and is relatively new to the marketplace. These trays are intended for large diameter and high pressure/high liquid loaded applications such as those found in Ethylene Production. Benchmarking the capacity and performance of such trays will be invaluable to the distillation industry. Operating data were taken both before and after the revamp and will be presented in the paper along with tray hydraulic information. This paper will address two main issues, capacity and performance of Shell HiFi™ Plus trays and the very important topic of comparing the new trays against the old 4-Pass tray design. Discussions will include the observed excellent tray efficiency, operational hydraulics and pressure drop of the new trays. In addition, unique features of the HiFi Plus tray will be discussed that enabled this tray efficiency to be achieved.

Extending Murphree Tray Efficiency from Mass to Heat Transfer in Distillation

In this work an extension of the well-known Murphree tray efficiency is proposed. In difference to the original model, vapor and liquid streams leaving the stage have different temperatures. In order to model the vapor temperature, the Murphree efficiency equation is used to calculate the change of vapor temperature between vapor inlet temperature and liquid outlet temperature, which will only be reached at full efficiency. As a result, vapor temperature will be much nearer to its dew point, which better matches reality.

Optimizing the Design of Splitter Towers

The abundance of affordable natural gas and continued growth in the utilization of ethylene and propylene derivatives are key drivers that are leading to the construction of large olefin plants. As is the case for most plants, the trend is to build ever larger olefin plants. To handle the capacity of these mega plants, large diameter splitter towers have to be designed and built. Novel trays and tray support structures were developed to meet these challenges. With these novel approaches, it was possible to build towers of more than 10 m in diameter without having the support structures interfering with the tray operation. Overall tray efficiency values in the range of 92 – 100 % were obtained in these splitter towers. This allowed the companies to minimize reflux ratios and maximize production rates.

Precise correlation of propylene-propane system and its analysis of relative volatility

In this research, a prediction method for the vapor-liquid equilibrium compositions of the propylene-propane mixture by the combined use of the COSMO-RS method and the Peng-Robinson equation of state is examined. Employing the van der Waals (VdW) mixing rule, the average deviations from this method for both the pressures and vapor phase compositions are no more than 0.62% and 0.75%, respectively. The average deviations for the relative volatility and tray efficiency are 0.93% and 5.52%, respectively. This method successfully describes the relative volatility of this system is not only related to the temperature but also dependent on the propylene mole fraction at low temperatures and high propylene concentrations. The density, excess molar volume and surface tension data are listed. The calculations explain the irregular phenomenon of the relative volatility. The results show that the non-ideality of this system comes from the dispersions between the components dominates the bulk liquid properties at low temperatures and high propylene concentrations.

CRITERIA OF EFFICIENCY ESTIMATION OF RECTIFICATION COLUMNS

This article deals with the efficiency of rectification columns which is often measured by the value of tray efficiency or single height of packing. The analysis of the factors influencing the efficiency of the rectification process was provided. This article shows that the commonly used Murphree efficiency factor in most cases estimates the efficiency trays and packing of the rectification process with a large error.

Application and performance analysis of the novel flow-guided vertical packing tray

In order to achieve higher throughput and better tray efficiency, this paper proposed a new type of flow-guided vertical packing tray, referred to as Novel FVPT, according to the design idea of composition. The novel tray was subjected to a cold mode experiment using an air-water (oxygen-enriched water) system in a 500 mm diameter Plexiglas column. The experiment included the clear liquid height, the dry pressure drop, the total pressure drop, entrainment, weeping and mass transfer efficiency. The correlation of the performance of the novel tray with the two-phase loading was invested in this work. Based on the mechanism of the pressure drop, the fundamental model of dry pressure drop of the novel tray was proposed. In addition, the industrial application of the novel tray was illustrated. The results showed that the novel tray with high throughout and better tray efficiency brought great economic and environmental benefits.

Hydrodynamics performance and tray efficiency analysis of the novel vertical spray packing tray

Abstract Column setup has been widely utilized in the petroleum and chemistry industries. However, with the fast progress of industries and the increasingly serious energy shortage, designing a new column setup with better performance and higher capacity becomes more urgent. In order to improve column's capacity and expand operating condition, a new type of column tray named novel vertical spray packing (NVSP) tray was designed and experimented. The performances of the novel tray, including pressure drop, weeping, entrainment and tray efficiency, were tested in a plexiglass column. In addition, performances of the novel tray were compared with that of the sieve tray and the Glitsch V1 valve tray. Based on the experiment data, the mathematical correlations of pressure drop, weeping and entrainment for the novel tray were established by regression analysis method. A fundamental model of dry pressure drop of the novel tray was promoted at the form of sum mode. The results indicate that the novel tray has wider operating condition and better performance.

A Multistage Fluidized Bed for the Deep Removal of Sour Gases: Proof of Concept and Tray Efficiencies.

Currently there are significant amounts of natural gas that cannot be produced and treated to meet pipeline specifications, because that would not be economically viable. This work investigates a bench scale multistage fluidized bed (MSFB) with shallow beds for sour gas removal from natural gas using a commercially available supported amine sorbent. A MSFB is regarded as a promising adsorber type for deep sour gas removal to parts per million concentrations. A series of experiments was conducted using carbon dioxide as sour gas and nitrogen to mimic natural gas. Removal below 3 mol ppm was successfully demonstrated. This indicates that gas bypassing is minor (that is, good gas–solid contacting) and that apparent adsorption kinetics are fast for the amine sorbent applied. Tray efficiencies for a chemisorption/adsorption system were reported for one of the first times. Current experiments performed at atmospheric pressure strongly indicate that deep removal is possible at higher pressures in a multistage fluidized bed.

Hydrodynamics and mass transfer performance of flow-guided jet packing tray

A new flow-guided jet packing tray (FJPT) with high flux and efficiency has been designed in this paper. Hydrodynamics and mass transfer performance of FJPT, including tray pressure drop, weeping, entrainment, clear liquid height and tray efficiency, have been studied with cold-flow model experiments (using water, air and other system other simulation system for the test in the absence of chemical reaction conditions), using air-water-oxygen system in a 500mm diameter plexiglass column. According to the experimental data, the empirical formulas of the FJPT have been established in terms of dry pressure drop and wet pressure drop. Compared with New Vertical Sieve Tray(New VST), FJPT has lower pressure drop. The experimental result shows that dry plate pressure drop is independent of the size of the gap, while bigger cap bottom gap leads to lower wet plate pressure drop and weeping percent, smaller bottom gap leads to less entrainment and higher tray efficiency. These have provided a good theoretical basis for the research and development of the compound tray.

PARAMETRIC INVESTIGATION OF FIXED-TRAY, SEMI-CONTINUOUS DISTILLATION COLUMN FOR ETHANOL SEPARATION FROM WATER

This work was aimed to evaluate the parameters affecting the separation of model fermentation broth (7 mole% ethanol) using 10-tray, semi-continuous distillation column. Ethanol compositions in distillate and bottoms were determined at different reflux ratios and feed locations. Results show that the distillation of lower ethanol concentration is better carried out at higher reflux ratio with feed charged at the middle or bottom tray for good overall tray efficiency. The distillation unit is able to purify the feed to 78 mole% ethanol in distillate. Through trial-and-error stepping off, about 81 mole% was predicted as optimum ethanol purity at reflux ratio of 2.33, while a lower reflux ratio of 1.44 was estimated for 78 mole%. Fixed-tray, semi-continuous distillation is a suitable option to concentrate fermentation broth with sufficient ethanol purity.

Sensitivity analyses and optimization of a gas sweetening plant for hydrogen sulfide and carbon dioxide capture using methyldiethanolamine solutions

The selective removal of hydrogen sulfide (H2S) in the presence of carbon dioxide using Methyldiethanolamine (MDEA) solutions is a significant process in the petroleum and natural gas industries. An industrial plant with an energy consumption of 3.36 GJ/mol CO2 was simulated and validated using rigorous kinetic and equilibrium models for H2S-CO2-MDEA-H2O system that are incorporated into the Amine Package in Aspen HYSYS®. A modified Murphee-type vapor tray efficiency of 15% for CO2 and 100% for H2S was utilized to account for the non-ideal behavior of the stages. Sensitivity analyses were performed on circulation rate (L/G = 0.6–2 kg/kg), stripper pressure (50–220 kPa), lean amine temperature (45–65 °C), number of absorber stages (8–14), and concentration of MDEA (15–50 wt%). These process variables were evaluated with respect to percentage recovery of sour gaseous components and normalized reboiler duty. The sensitivity analyses results showed that the circulation rate and the MDEA concentration are the two main factors improving process performance. The optimized scenarios exhibited better selective H2S absorption and higher energy savings.

Numerical modeling of heat and mass transfer efficiency of the processes in turbulent foam layers in distillation

A closedmathematical description of the fields of velocities, concentrations, and temperatures on a contact cross-flow tray was obtained via simultaneous application of a two-dimensional system of differential energy, mass, and momentum transfer equations (written for liquid phase of a turbulent bubble layer with regard to gas interaction) and equilibrium and balance equations. The paper presents results of numerical solving this system and comparison with experimental data on the velocity field, concentration and temperature fields in distillation of various mixtures. Results of calculating the heat and mass transfer efficiency of bubble trays are also presented.

Hydrodynamics and mass transfer performance of vapor–liquid flow of orthogonal wave tray column

In the present work, hydrodynamics and mass-transfer performance of vapor–liquid flow of orthogonal wave tray (OWT) column was studied. Dry pressure drop, operating range (capacity graph) and overall column efficiency of OWT column were investigated using pilot columns. A three-dimensional CFD model was developed within the two-phase Eulerian framework to have an insight into the two-phase flow and mass-transfer behavior of OWT. The simulated results were compared with experimental data and showed a good agreement. Hydrodynamic and mass-transfer behaviors were revealed with the aid of velocity profiles, streamlines, interfacial area density distribution and so on. The effects of vapor/liquid load (FS factor) on the Murphree tray efficiency were also studied. The simulations of OWT with different waves showed that the pressure drop, clear liquid height, froth height and Murphree tray efficiency increase with the increase of slope, and OWT with middle slope tended to have more uniform foam layer. Comparison of the liquid-phase component velocity between OWT and ripple shows that OWT has better performance in froth layer distribution and stability. The mass-transfer data showed that OWT not only had almost the same “peak efficiency” as sieve tray, but also had higher capacity and stability, it was suitable for capacity expansion.

New Realization of Periodic Cycled Separation

A new realization of periodic cycled gas/liquid separation is presented. Separation factors and column efficiencies are compared for a column stripping ammonia from water with air, using three different sets of internals: conventional sieve trays, Sulzer BX gauze packings, and periodically cycled trays. The proposed new periodic trays are shown to be advantageous compared to their continuous alternatives. It is demonstrated experimentally that periodic tray efficiencies of up to 300% are achievable. With the proposed new tray design, a new operation form is also introduced in which the trays are drained sequentially rather than simultaneously, such that the vapor flow is not interrupted during the liquid drainage. For different ratios of counter-current vapor/liquid flow rates, column efficiencies for periodically cycled columns are shown experimentally to be two times greater than those for columns with sieve trays.